As shown in FIG. 8, a conventional internal groove insert, which is mounted to a tool holder, is used to form a groove inside a bore of a workpiece. As further shown in FIG. 8, the conventional internal groove insert 100 includes a main body 110 and two projections 121, 122 that project from two adjacent lateral surfaces of the main body 110. Thus, the insert 100 generally has an L-shape. Cutting edges 124, 126 for performing a cutting operation are formed at the end portions of the two projections 121, 122. The insert 100 having such a shape is mounted within a pocket formed at the end portion of a tool holder 130, wherein the pocket has a shape corresponding to the insert 100 so that it can accommodate the insert 100 therein. That is, the pocket is provided with a recess 132, which corresponds to and receives one of the projections of the insert 100. As the tool holder 130 in which the insert 100 is mounted rotates about a rotation axis 134, the cutting edge 124 projecting outwardly from the peripheral surface of the tool holder 130 cuts the interior surface of the bore of the workpiece 136 such that a groove can be formed.
FIG. 9 shows a conventional indexable cutting insert 200, which is capable of both turning and drilling. As shown in FIG. 9, the cutting insert 200 includes a top surface 201, a lower surface 202 and four lateral surfaces 203 extending between the top surface 201 and the lower surface 202 so that the insert 200 has a generally rectangular shape. The lateral surface 203 of the cutting insert 200 is configured to be inclined by an obtuse angle with respect to the lower surface 202 so as to define a positive clearance angle. As such, when performing turning and drilling operations, it can avoid an interference with a workpiece. FIG. 10 is a side view of the end portion of a tool holder having the cutting insert of FIG. 9. As shown in FIG. 10, a lateral wall 212 of a pocket of the tool holder 210, in which the insert 200 is mounted, is inclined by an obtuse angle with respect to the bottom surface 214 of the pocket. The obtuse angle between the lateral wall 212 and the bottom surface 214 is same as the angle α between the lateral surface 203 and the lower surface 202 of the cutting insert 200.
As such, the internal groove insert and the indexable cutting insert for turning and drilling have different shapes since their operating conditions differ. Further, a pocket of a tool holder is configured to have a shape, which may receive its corresponding insert. Thus, the conventional technique has a problem in that the tool holder for the conventional indexable cutting insert for turning and drilling cannot be used for an internal groove insert. Moreover, a separate tool holder, which is different from the tool holder of the conventional indexable insert for turning and drilling, is required for the internal groove insert.